Fabrication of poly(ethylene-co-vinyl acetate) (EVA)/biomass composite using residual Chlorella biomass through a sequential biorefinery process

Abstract

Realization of full-fledged microalgae-based bioeconomy hinges on implementing integrated biorefineries, in which multiproducts are recovered from intact biomass with a minimal amount of waste materials. In particular, existing literature has suggested identifying correct valorization pathways for residual biomass generated following extraction or conversion processes as a key innovation necessary for microalgae-based biorefineries. This study aimed to evaluate the possibility of utilizing different biomass materials recovered from the operation of sequential microalgal biorefinery, through which lipid and carbohydrate portions of intact Chlorella biomass are sequentially removed via solvent extraction (defatting) and dilute acid hydrolysis (desugaring). Three types of biomass materials, including intact Chlorella biomass, were first analyzed for biochemical composition: the results indicated a proportional increase in protein and carbohydrate following the defatting step because of the removal of lipid fraction, while a significant increase in the amount of crude protein was further observed after the saccharification of 100 g/L of dried defatted biomass with varying concentrations of HCl between 0.1 N and 0.5 N. Provided that the results of FTIR analysis suggested a distinctive increase in peaks corresponding to the functional groups of protein in defatted and desugared biomass, the fabrication of poly(ethylene-co-vinyl acetate) (EVA)/biomass composite indicated substantial improvements in the mechanical properties of composites formulated with defatted and desugared biomass compared to the composite fabricated with intact Chlorella biomass at a biomass blend ratio of 30 wt.%. Although lipid extraction seemed to have a minimal influence on the mechanical properties of the composite, the results suggested that the saccharification process can be favorably considered in the design of microalgal biorefinery aiming to produce plastic filler materials. Given that an increase in the acid concentration during the desugaring step did not lead to a commensurable improvement in the mechanical properties of the final composites, continuing efforts are warranted to maximize the overall economic outlook of the biorefinery process simultaneously utilizing both hydrolysate, as well as the leftover residual materials under optimized operation strategies.